A PSA (Polymer Sustained Alignment) type liquid crystal display element has a structure with a polymer structure formed in a cell in order to control a pretilt angle of a liquid crystal molecule, and has been practically used as a liquid crystal display element due to high speed responsiveness and high contrast.
Production of a PSA type liquid crystal display element is performed by injecting a polymerizable composition containing a liquid crystal compound and a polymerizable compound between substrates, and polymerizing the polymerizable compound to fix the alignment of liquid crystal molecules in a state of applying a voltage to the polymerizable composition and aligning the liquid crystal molecules. As the cause of image sticking which is a display defect of the PSA type liquid crystal display element, impurities and change in alignment of the liquid crystal molecules are known (change in pretilt angle).
In the image sticking due to the change in the pretilt angle of liquid crystal molecules, the change in the pretilt angle is a result of change in the structure of a polymer when the same pattern is repetitively displayed for a long period of time as the case of constituting the display element. Therefore, a polymerizable compound forming a polymer having a rigid structure with no change in the polymer structure is required.
In the related art, in order to prevent the image sticking by improving the rigidity of a polymer, configuring a display element using a polymerizable compound which includes a structure such as a 1,4-phenylene group composed only of a ring structure and a polymerizable functional group and configuring a display element using a polymerizable compound having a biaryl structure (Patent Documents 1 to 4) have been considered. However, since the polymerizable compounds have low compatability with respect to a liquid crystal compound, deposition of the polymerizable compound occurs when a liquid crystal composition is prepared, therefore, improvement thereof is required.
Further, when a biaryl-based polymerizable compound is polymerized using UV irradiation, for example, the reaction speed is low, so UV irradiation time is needed to be longer. However, when the UV irradiation time becomes longer, decomposition or the like of the liquid crystal composition occurs, and this leads to degradation in reliability.
As described above, it is difficult to satisfy characteristics, which are required in a polymerizable-compound-containing liquid crystal composition, such as image sticking of a display element, alignment stability, stability as a liquid crystal composition with no deposition occurring, a display characteristic, and manufacturing efficiency when a PSA type liquid crystal display element is prepared, therefore, further improvement is required.